Introduction: Morphea is a chronic autoimmune disease characterized by fibrosis of the skin. Dendritic cells (DC) and regulatory T cells (Tregs) play a significant role in development of autoimmune and tolerance mechanisms. The aim of the study was to establish the expression of selected genes of plasmacytoid and myeloid DC, Treg cells, and the microenvironment of cytokines (interleukin-17A (IL-17A), transforming growth factor  (TGF-)) in blood and skin of morphea patients. In addition, the effect of UVA1 phototherapy on expression of the aforementioned genes was evaluated.

Material and methods: The study was performed on 15 blood and 10 skin samples from patients with morphea. The evaluation included expression of CLEC4C (C-type lectin domain family 4, member C receptor), Lymphocyte antigen 75 (LY75), Forkhead box p3 (foxp3) transcription factor, IL-17A and TGF- genes in peripheral blood mononuclear cells (PBMC) and in skin samples both before and after UVA1 phototherapy using real-time polymerase chain reaction.

Results: The study revealed lower expression of CLEC4C before (p = 0.010) and after (p = 0.009) phototherapy and lower expression of IL-17A before (p = 0.038) phototherapy in PBMC of patients with morphea vs. the control group. Expression of CLEC4C in PBMC correlated negatively (rho = –0.90; p = 0.001) with activity of disease after phototherapy. No significant differences were found between expression of analysed genes before and after UVA1 therapy in PBMC and skin of morphea patients.

Conclusions: The results do not confirm the involvement of analysed subsets of DC and Tregs in UVA1 phototherapy in morphea, but point to CLEC4C as a possible biomarker associated with the disease activity.